Abstract
The synthetic AVP analogue 1-desamino-8-d-arginine-vasopressin (dDAVP) is used for treatment of polyuric disorders. Lack of commercially available assays limits the usefulness of dDAVP as a diagnostic tool in the assessment of renal concentrating capacity. We aimed to develop a specific radioimmunoassay (RIA) for determination of plasma dDAVP (pdDAVP) in order to investigate the relationship between pdDAVP levels and urine osmolality (Uosm). Further, we aimed to determine the onset, duration, and maximum concentrating capacity following intravenous (i.v.) bolus dDAVP injection. The dDAVP assay was based on a well-established RIA for measurements of AVP. Fourteen healthy subjects (aged 15-18 years) participated. Blood and urine samples were collected prior to and after i.v. bolus of 0.03 µg/kg dDAVP. Diuresis and Uosm was measured for nine hours following dDAVP administration. PdDAVP and Uosm were analyzed.We established a specific RIA for the measurement of pdDAVP. All subjects reached maximal pdDAVP concentration (Cmax) 30 minutes following infusion, and a rise in Uosm after 60 minutes. Maximal Uosm varied between subjects, with no direct correlation to the achieved pdDAVP levels. We found no significant intra-individual variation between two dDAVP infusions and the effect was reproducible in terms of Cmax and maximal Uosm. We characterized the relationship between pdDAVP and Uosm after dDAVP bolus injection in healthy adolescents using our dDAVP assay. Maximal Uosm achieved correlated with the baseline Uosm levels and seemed unrelated to achieved pdDAVP levels. The urine concentrating response was maintained at least eight hours.
